1. Field of the Invention
This invention relates to the field of disk drives, in particular to reclaiming disk drive head gimbal assemblies.
2. Description of Related Art
A disk drive generally uses one or more spinning storage disks, sometimes called storage media, to store data. Disks can be rigid, as used in hard drives, or flexible, as used in floppy drives. Disks commonly store data using magnetic methods or optical methods, and can spin at rates exceeding 15,000 revolutions per minute (rpm). Hard disk drives generally employ several rigid disks stacked one on top of another with spaces in between, attached to a common spindle. Floppy disk drives generally employ a single flexible disk in a bonded sleeve.
Over the surface of each disk in a disk drive, commonly on both sides of each disk, a read-write head is suspended in close proximity to the disk surface by a disk drive suspension. A disk drive suspension is sometimes referred to as a disk drive head suspension or simply a suspension. In hard disk drives with multiple disks on a spindle, suspensions operate in the spaces between the disks and on the two outer disk surfaces. A suspension is a cantilever beam-like feature, mounted on a movable actuator arm. The suspension extends to a precise but variable location above a disk. A suspension typically includes a mounting region, a hinge, load beam, gimbal, and flexure.
The combination of a suspension as discussed above and a read-write head is sometimes called a suspension assembly or a head gimbal assembly (HGA).
The load beam is a major arm-like part of the suspension which forms part of its structural backbone. An actuator arm supports the load beam at the load beam's proximal end, and the load beam supports the flexure at the load beams' distal end. The term “load beam” refers to a structure which may be unitary or may be composed of separately formed parts which are later affixed to one another.
The gimbal is held by the load beam over the disk. The gimbal retains the read-write head in a precise position near the load beam distal end while allowing the read-write head to pitch and roll slightly. A gimbal can be an integrally formed portion of a load beam, or it can be a separately formed part.
The flexure is typically referred to as a wiring layer or a circuit or one of several branded terms, i.e. Integrated Lead Suspension (ILS), Flex On Suspension (FOS), Integrated Lead Flexure (ILF), Electrical Lead Suspension (ELS), or Additive Circuit Gimbal (ACG). The flexure electrically connects the read-write head, located at the distal end of the suspension, to disk drive circuits at the proximal end of the head suspension. An electrical interconnect, sometimes referred to as “electrical leads,” is supported by the flexure and is often integrally formed with the flexure. The electrical interconnect carries electrical signals from the read-write head that are read from the disk across the suspension to disk drive circuitry. The flexure also carries electrical signals to be written to the disk from the disk drive circuitry across the suspension to the read-write head. The flexure can be integrally formed on a load beam.
The read-write head, also referred to as a head or a “slider,” contains read-write transducer circuitry upon its proximal end. The slider surface facing the disk is designed and reactive-ion etched to define an aerodynamic pattern typically comprising rails that, in conjunction with the spinning disk, generate a positive pressure thereby lifting the slider from the spinning disk surface. The wind of the rapidly spinning disk running past an aerodynamic pattern of protrusions on the slider creates the air bearing surface (ABS) that enables the slider to fly at a constant height close to the disk during operation of the disk drive. The resultant boundary layer of air is commonly called an air bearing. The gram force of the load beam hinge pushes the slider toward the disk while the air bearing of the disk pushes away until an equilibrium position is reached. The equilibrium position is designed to be close enough to the disk so that the slider's read-write circuitry can interact with the disk but far enough away to prevent mechanical contact.
The slider is commonly a magnetic head which is typically formed from a wafer compound of a multi-layer substrate. The slider is attached onto a tongue area of the suspension, typically using a small amount of epoxy between the slider and suspension tongue. Solder balls or gold balls are then bonded between the slider pads and the suspension pads. These solder or gold balls, sometimes called “bonding balls,” transfer electrical signals between the suspension and the slider.
The manufacturing process of assembling HGAs by adhering a slider to a disk drive head suspension, or “suspension” for shorthand, and soldering their electrical contacts with solder or gold balls is well known in the art. After assembly, testing can indicate a problem with the slider or read/write head on the slider. If testing reveals a problem with the slider, either because of a defect or electrostatic discharge (ESD) damage to the slider, the defective slider can be removed and the suspension reused. The process of removing a defective slider from a suspension is sometimes called a “suspension reclaim method” or “reworking a head gimbal assembly.”
A common prior art suspension reclaim method is to use a cutter to cut the gold balls or solder balls which electrically connect the slider and suspension electrical trace pads. This is sometimes called a “cutting method.” This method is labor intensive and the reclaim yield is not high. For gold balls, the results of this method can be adequate; however, for solder balls, this method has been found to have serious deficiencies.
Solder balls are often smaller than their gold ball counterparts and so are more difficult to work with. Additionally, solder balls are fully connected with the bonding pads and there is a layer of relatively hard intermetallic compound (IMC), generally consisting of AuSn2 and AuSn4, between the solder balls and metal terminal pads. Thus, it can be very difficult to remove solder balls by the cutting method. Because the IMC layer is very hard and the solder balls fully contact the slider pads and suspension pads, cracks sometimes develop in flexure terminal pads after removing solder balls and sliders from suspensions.
U.S. Pat. No. 7,296,335 to Thaveeprungsriporn et al. and assigned to the assignee of the present invention discloses a prior art suspension reclaim method which uses ultrasonic energy. Ultrasonic energy, or oscillations, can weaken bonding balls. In Thaveeprungsriporn, an ultrasonic probe is placed in contact with or near to the connection (i.e. bonding balls) between the slider and the gimbal and the slider is separated from the suspension. However, due to the extremely delicate nature of the connections and labor-intensive use of an ultrasound machine, an improved method of using ultrasonic energy is sought.